Exhaust pipe with tubular sound attenuating chamber-forming means disposed therein



Oct. 4, 1966 F. E. DEREMER 3,275,541

EXHAUST PIPE WITH TUBULA OUND ATTENUATING CHAMBER-FORMING MEANS SPOSEDTHEREIN Original Filed Oct, 3, 1962 I 2 Sheets-Sheet 1 IN V EN TOR. FL.0217 E. ZZEREMEH /M: QM

A TTORNEY 3,276,541 TENUATING CHAMBER-FORMING MEANS DISPOSED THEREINOriginal Filed Oct. 3, 1962 2 Sheets-Sheet 2 Oct. 4, 1966 F. E. DEREMEREXHAUST PIPE WITH TUBULAR SOUND AT INVENTOR: I FLUYJJ E. .UEREMEH. BY

J40 a, a/MMM ATTORNEY United States Patent 3 276,541 EXHAUST PIPE WITHTUBULAR SOUND ATTEN- UATING CHAMBER-FORMING MEANS DIS- POSED THEREINFloyd E. Deremer, Livonia,

Manufacturing. Company,

Mich., assignor to Oldherg Grand Haven, Mich, a corporation of MichiganOriginal application Oct. 3, 1962, Ser. No. 228,131, now Patent No.3,219,142, dated Nov. 23, 1965. Divided and this application Oct. 1,1965, Ser. No. 492,107

7 Claims. (Cl. 18148) the exhaust gases conveyed from the mufflerthrough a,

tail pipe rearwardly of the vehicle. The muffler or silencers heretoforeused are usually of from two to four feet in length depending upon theinterior gas passage and sound attenuating construction of the mufflerunit. The efficiency of sound attenuation of sound waves in an exhaustgas stream is dependent in a large measure upon the provision of soundattenuating means of a character which will attenuate or dampen soundwaves of various lengths, some low frequency sound waves being of alength of several feet.

Muffiers or silencers have been constructed of substantial length tofacilitate straight through flow or passage of the gases through themuffler and such installations were used in vehicles where a space ofsuificient length was available to accommodate such installations. Thetrend toward lowering the vehicle silhouette and the use of multipleframe or transverse bracing means or members beneath the vehicle floornecessitated shortening of the mufiler or silencer units. In order toobtain a reasonable length of gas travel for sound attenuating purposes,mufiler units have been made having internal gas passage tubes arrangedto reverse the travel of the gas through the muffler in a Sshaped path,a construction which necessarily increases exhaust gas back pressure aswell as entailing difficulties in cooling and rapid deterioration of thegas passage means. Such muffler units in many instances provide aninsufficient length of gas travel for proper sound attenuation and hencethe use of supplemental muffier or resonators have been employed inconjunction with primary mufiier units and spaced therefrom in anendeavor to secure more efiicient sound attenuation. Such arrangementsor installations are costly and fail to satisfactorily attenuate many ofthe longer sound waves in the gas streams.

The present invention embraces a method or system providing for greatlyincreased length of gas passage means associated with sound attenuatinginstrumentalities whereby to obtain more efficient sound attenuation andparticularly attenuation of sound Waves of substantial lengths andeffect a substantial reduction in back pressure.

An object of the invention is the provision of a method of or system forimproving sound attenuation in an exhaust gas stream of an automotivevehicle wherein the gases move generally in one direction throughlengthwise spaced sound attenuating media with a minimum of exhaust gasback pressure and providing for improved sound attenuation.

Another object of the invention is the provision of a sound attenuatingmeans particularly for attenuating sound waves in an exhaust gas streamfrom an internal combustion engine in an automotive vehicle wherein thegases are conveyed from an exhaust manifold through a single tubularmeans to the rear of the vehicle with resonators or sound attenuatingmeans spaced lengthwise with in the tubular means whereby sound waves ofvarying lengths may be satisfactorily attenuated.

Another object of the invention resides in the provision of a combinedexhaust pipe and sound attenuating media facilitating conveyance ofexhaust gases generally in one direction thereby eliminating reverseflow of gases whereby deposits of particulate material resulting fromcombustion entrained in the exhaust gases are substantially eliminated.7

Another object of the invention is the provision of a single tubularmeans or pipe for conveying an exhaust gas stream away from an internalcombustion engine wherein a plurality of sound attenuating units orresonators are arranged in spaced relation for attenuating sound wavesentrained in the gas stream, the spacing between individual resonatorsor sound attenuating means being such that objectionable sound waves maybe tuned out, attenuated or absorbed.

A further object of the invention resides in the provision of a tunedexhaust pipe or system comprising a combined exhaust pipe and soundattenuating means or media of substantial length embodying spacedresonators within the pipe, the pipe being of substantial length wherebypressure impulses in the gas stream are more effectively equalizedthereby minimizing the throbbing usually attendant the discharge ofexhaust gases from a conventional muflier and exhaust pipe.

A further object of the invention resides in the provision of a singleexhaust conveying tube of substantial length embodying spaced soundattenuating devices or resonators arranged whereby the pipe may beconfigurated to avoid interference with structural components of thevehicle yet providing for movement of the gases generally in onedirection from the exhaust manifold of the engine for dischargerearwardly of the vehicle.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, op eration and function of therelated elements of the structure, to various details of constructionand to combinations of parts, elements per se, and to economies ofmanufacture and numerous other features as will be apparent from aconsideration of the specification and drawing of a form of theinvention, which may be preferred,

in which:

FIGURE 1 is a phantom or schematic view of a unitized type of frameconstruction of an automotive vehicle embodying an internal combustionengine and illustrating a form of tuned exhaust pipe or soundattenuating system of the invention;

FIGURE 2 is an elevational view of the sound attenuating or tunedexhaust pipe or tube illustrated in FIGURE 1 showing the soundattenuating media or resonators in spaced relation;

FIGURE 3 is an elevational view of an exhaust pipe embodying spacedresonators illustrating one method of configurating or bending astraight pipe at regions spaced from the resonators to avoidinterference with frame or structural components of the vehicle withwhich the pipe may be used;

FIGURE 4 is a longitudinal sectional view illustrating one form ofcombined exhaust pipe and resonator or sound attenuating mediacomprising a series of sound attenuating units in end-to-end relationand Welded to provide a continuous tubular construction;

FIGURE 5 is an enlarged sectional view taken substantially on the line55 of FIGURE 4;

FIGURE 6 illustrates another method of forming a continuous tunedexhaust utilizing tubular couplings between adjacent sound attenuatingunits;

FIGURE 7 is a longitudinal sectional view illustrating a one piecetubular exhaust pipe embodying spaced sound attenuators or resonatorswherein regions of the exhaust pipe are distorted or spun inwardly tosecure the resonators in proper position in the exhaust pipe;

FIGURE 8 is an elevational view of tuned exhaust pipe embodying soundattenuator or resonator units telescoped in the exhaust pipe;

FIGURE 9 is an enlarged transverse sectional view taken substantially onthe line 9-9 of FIGURE 8, and

FIGURE 10 is a sectional view illustrating an exhaust pipe embodyinganother form of resonator or sound attenuating means.

The combined exhaust pipe and sound attenuator construction or tunedexhaust tube has particular utility with vehicle constructions poweredby internal combustion engines as the arrangement of the inventionprovides effective length for attenuation of sound waves of varyinglengths, the tube being configurated to avoid interference withstructural components of the vehicle. It is to be understood that themethod and arrangement of sound attenuation and gas conveying means ofthe invention may be used wherever it may be found to have utility.

Referring particularly to FIGURE 1, there is illustrated in phantom orschematic form a vehicle frame 10 of so-called unitized constructionpreferably formed of sheet metal shaped to the desired configuration bysuitable dies, the frame construction embodying a forward panel orengine mounting portion 12, an intermediate raised portion 14 toaccommodate power transmission means and a transversely raised portion16 to accommodate vertical movements of the rear axle or axles of thevehicle. The body construction 10 is fashioned with lengthwise extendingside flanges 18 to lend rigidity or stiffness to the frame constructionand transversely arranged reinforcing members.

The forward portion 12 of the frame construction supports an internalcombustion engine 20 which, in the embodiment illustrated, is of theV-type construction embodying two banks of cylinders indicated at 22 and24. The bank of cylinders 22 is provided with an exhaust manifold 26having an exhaust pipe connection 28. The bank of cylinders 24 isprovided with an exhaust manifold 30 fashioned with an exhaust pipeconnection 32. In the embodiment illustrated, the exhaust pipeconnections 28 and 32 are joined respectively with portions 34 and 36 ofa dual or Siamese pipe or coupling construction 38.

In the arrangement shown in FIGURE 1, the gas streams from both banks ofcylinders are converged into a single combined exhaust pipe and soundattenuating construction or tuned exhaust pipe 40. The exhaust pipeconstruction extends to a region at the rear of the vehicle and theexhaust gases are discharged from the distal end 41 of the tuned exhaustpipe.

In the embodiment illustrated in FIGURE 1, the exhaust gas streams fromboth banks of cylinders are combined for conveyance through the singletuned exhaust pipe 40. It is to be understood however that a separatetuned exhaust pipe may be employed for each bank'of cylinders ifdesired. The use of a single exhaust pipe 40 or two exhaust pipes ofsubstantially identical character, one for each bank of cylinders, isdependent upon the volume of exhaust gases to be conveyed through thetuned exhaust pipe construction.

The exhaust pipe arrangement 40 may be a single full length tube or anassembly of individual lengths of tubing welded or otherwise securedtogether as hereinafter described. The pipe 40, as shown in FIGURES 1through 3, embodies three sound attenuators or resonator units 42, 44and 46 arranged in lengthwise spaced relation, the relative positions ofthe units depending upon the available space adjacent the vehicle frameand body to accommodate the sound attenuating units and the particularpositioning of the sound attenuating units to obtain the desired soundattenuation or sound absorption.

In the tuned exhaust pipe construction shown in FIG- URES 1 through 3,the exhaust pipe has a bent region at 50 between adjacent resonators 42and 44 and a second bent region adjacent the raised portion 16 of thevehicle frame to avoid interference with the vertical movement of therear axle or axles of the vehicle. The bent zones at the regions 50 and52 may be fashioned in the exhaust pipe or tube by means of a suitablebending tool 54 or the bends may be fashioned in the tube by diesthrough the use of a press. 7

The exhaust gases enter the forward end of the tube 40 and travel in arearward direction, the only deviation in rectilinear travel being thepath of traverse at the bends 50 and 52 or other bent regions that maybe fashioned in the exhaust pipe and through sound attenuation cham bersor regions adjacent gas passage means in the sound attenuating unitshereinafter described.

It is to be understood that while two bent regions 50 and 52 areillustrated in FIGURES 1 through 3, other bends may be fashioned in thepipe to avoid interference with components of the vehicle frame or bodyconstruction. The resonators or sound attenuating units 42, 44 and 46are preferably disposed in rectilinear regions of the exhaust pipe andmay be spaced as desired to secure most effective sound attenuationcharacteristics or tuning as the bent regions which are not readilysusceptible for accommodating the sound attenuators. It is to beunderstood that the sound attenuators or attenuating units may be ofvarying lengths depending upon the character of sound wave attenuationor sound wave damping desired.

FIGURE 4 is illustrative of a tuned exhaust pipe or combined exhaustpipe and sound attenuator construction 56 which is made up of severalresonator units of a particular type of construction, the ends of theunits being welded together, either in abutted relation or inoverlapping telescoping relation, so that the final assembly is acontinuous tubular means with spaced sound attenuators or attenuatingunits. The pipe 56 has four sound attenuating units designatedrespectively 57, 58, 59 and 60 which may be in spaced relation, thespaces between adjacent units being dependent upon the length requiredfor bends or distorted regions in the pipe.

The sound attenuating unit 57, in the form illustrated, comprises acentral tubular member or inner shell 62 forming a gas passage means,the wall of which is provided with a comparatively large number of smallopenings forming acoustic couplings 64.

The outer tube, shell or tubular portion 66 of the attenuating unit 57is distorted or spun inwardly at peripheral regions 68 to engageinwardly extending annular ridges thus formed on the shell with theexterior surface of the inner shell or tubular member 62. Through thisarrangement sound attenuating chambers 70 and 7-2 are formed which areacoustically coupled with the inner shell 62 through the small openings64, the annular chambers or regions 70 and 72 functioning to attenuatesound waves.

The sound attenuating unit 57 may be butt welded to the adjacentresonator 58 at the region indicatedat 74 to form a continuation of theouter tube 66 with the outer tube of the sound attenuating unit 58. Ifdesired, one end region of the outer tube of an attenuating unit may beof slightly larger diameter to be telescoped with the end region of theadjacent unit and the overlapping regions welded or sealed in a suitablemanner to form a continuous imperforate outer shell or exhaust pipe.

The sound attenuating unit or means 58 may be formed with an inner shellor inner gas passage tube 78 and the outer tube or shell 76 may be spunor distorted inwardly at lengthwise spaced regions designated 80, 81

.and 82 into engagement with the outer surface of the inner shell 78 toprovide sound attenuating chambers 84 and 86.

The inner shell 78 is acoustically coupled with the annular chambers orregions 84 and 86 through a comparatively large number of small openings88 formed in the Wall of the inner shell 78. The sound attenuatingchambers 84 .and 86 may be of varying lengths depending upon the spacingof the inwardly extending peripheral regions 80, 81 and 82 of the outershell or tube 76.

The sound attenuating unit 58 may be coupled with the adjacent unit 519by butt welding at the region indicated at 90. The sound attenuatingunit 59, in the illustration of FIGURE 4, includes an inner shell ortube 92 which is disposed centrally of the outer shell or tube 94 by theinwardly spun or distorted regions 96 and 98 to form a comparativelylong sound attenuating chamber 100 of a length defined by the inwardlyextending portion 96 and 98. The inner tube or gas passage means 92 isacoustically coupled with the chamber 100 through a comparatively largenumber of small openings 102 formed in the wall of the inner shell 92.

In the unit illustrated at 59 a single sound attenuating chamber 100 isprovided for attenuating sound waves. The sound attenuating units may beprovided with restriction means to pro-mote increased flow of exhaustgases through the annular sound attenuating chambers if desired. In theembodiment illustrated in FIGURE 4, the sound attenuating unit 59 isprovided with a member or restrictor 104 disposed in the inner shell 92.The restrictor 104 may be in the form of an .annularly shaped member ora short length tube preferably having a tapered portion 105 whichdefines a restricted passage in the restrictor 104.

The restrictor promotes increased flow of exhaust gases through theopenings 1022 at the left side of the restrictor, as viewed in FIGURE 4,for traverse through the chamber 100, such gases reentering the innershell 92 through the openings 102 at the right side of the restrictor.It is to be understood that in the absence of a restrictor some gas flowtakes place through the sound attenuating chambers surrounding the innershells or gas passage tubes of the attenuators and such flow of exhaustgases through the sound attenuating chambers tends to equalize thetemperatures and to reduce the temperatures by reason of the heatradiated or conducted from the gases through the outer walls of theunits.

The outer tube or shell 94 of the sound attenuating unit 59 may bewelded to the outer tube 108 of the adjacent unit 60 at the regionindicated at 110. In the embodiment illustrated in FIGURE 4, the soundattenuating means or unit 60 includes an inner shell or gas passage tube112 which is centrally spaced in the outer tube 108 by inwardlyextending regions or ridge portions 114 and 116 formed in the outer tube108. The region between the portions 114 and 11 6 and between the innershell 1 12 and the tube 108 provides a sound attenuating chamber 1:18 ofsubstantial length.

In the embodiment illustrated the wall of the inner shell 112 may beprovided with comparatively few openings 120 of larger size tofacilitate increased flow of exhaust gases through the chamber 118, theopenings 120 forming acoustic couplings with the chamber 118.

The exhaust gases may be discharged from the distal end 122 of the soundattenuating unit 60 or may be conveyed away by a tail pipe (not shown)connected with the end of the unit 60.

While the various forms of sound attenuating unit, illustrated in FIGURE4, are arranged in rectilinear alignment, it is to be understood thatthe regions between adjacent resonators may he of substantial length andsuch regions may be provided with bends as shown in FIGURE 2 to avoidinterference with components of the vehicle frame construction. Whilethe sound attenuating units are illustrated in FIGURE 4 as directlycoupled together by welding as hereinbefore described, it is to beunderstood that the units may be spaced apart by tubular inserts orcouplings of substantially the same diameter as the outer tubecomponents and such inserts may be bent or configurated to avoidinterference with frame components of the vehicle construction.

A construction of this character is illustrated in FIG- URE 6. In thisfigure a sound attenuating unit 124, which may be of any of the typesherein shown or described, is interiorly telescoped into the end regionof a tubular coupling member or insert 126 employed for coupling twoattenuating units together. As shown in FIGURE 6 the coupling member orinsert 126 may be bent or configurated to a desired shape to avoidinterference with components of the vehicle frame construction.

The overlapping region 128 of the sound attenuating unit 124 and thecoupling member or insert 126 may be welded, crimped or otherwise.processed to form a sealed joint between the sound attentuator unit 124and the coupling member 126.

Another form of combined exhaust pipe and sound attenuating constructionor tuned exhaust pipe is illustrated in FIGURE 7. In this form, theexhaust pipe, outer tube or shell 130 may be a continuous tube anddisposed units may be provided Within the tube. The inner shells 132,134 and 136. An additional number of attenuating units may be providedwithin the tube. The inner shells may be of varying lengths dependingupon the sound attenuating characteristics desired and the availablerectilinear space beneath the vehicle frame or body construction.

The outer tube 130 may be distorted or spun inwardly at space regionsinto engagement with the adjacent inner shell to form sound attenuatingchambers. In the embodiment illustrated, the tube 130 is distortedinwardly at regions illustrated 138, 139 and 140 providing with theinner and outer tubular components, partitions defining soundattenuating chambers 142 and 144. The chambers 142 and 144 areacoustically coupled with the inner shell 132 through a plurality ofsmall openings 146.

The outer tube 130, at the region of the inner shell 134, may be spun ordistorted inwardly at regions designated 148, 149 and 150 providingpartitions forming sound attenuating chambers 152 and 154 which areacoustically coupled with the inner shell through a large number ofsmall openings 156 formed in the wall of the inner shell 134.

The inner shell 136 may be secured in its central position within thetube 130 by spinning or distorting the tube inwardly at the regionindicated at 160 and additional regions spaced therefrom (not shown) toform a third sound attentuating unit.

While the regions between adjacent attenuators illustrated in FIGURE 7are of rectilinear shape, it is to be understood that these regions maybe bent or distorted as hereinbefore described to avoid interferencewith frame components of the vehicle. In this form of construction, theouter tube 130 is a single component and is imperforate throughout itslength. The arrangement illustrated in FIGURE 7 is adapted to attenuatesound waves in the same manner as in the other forms of the inventionhereinbefore described.

Another form of combined exhaust pipe and sound attenuating means ortuned exhaust tube is illustrated in FIGURES 8 and 9. In this form anexhaust pipe or tube 166 may be a single component and individual soundattenuating units of any of the forms illustrated in FIG- URE 4 or 10may be inserted in the tube 166 and spaced lengthwise therein as desiredto secure desired sound attenuating characteristics. In the form shownin FIGURE 8, three sound attenuating units designated 168, 170 and 172are arranged in spaced relation, the spacing depending upon the regionsof the tube 166 to be bent or distorted to avoid interference with framecomponents of the vehicle.

The sound attenuating unit 168 may be of the character illustrated at 57in FIGURE 4 comprising an outer shell 174, an inner shell 176, andspaced peripheral regions 178, 179 and 180 distorted or spun inwardlyinto engagement with the inner shell 176 providing partitions definingsound attenuating chambers 132 and 184, which are acoustically coupledwith the interior of the inner shell 176 through a plurality of openings190 formed in the wall thereof. The other attenuating units 170 and 172may be of the same or similar construction or may be of any of the otherconstructions herein disclosed and described. Each of the attenuatingunits may be spot welded at regions indicated at 192 to assure retentionof the units in proper spaced relation in the exhaust pipe or outer tube166.

Another form of sound attenuating unit, that may be used in conjunctionwith the same or similar attenuating units or which may be inserted inan exhaust pipe in the manner illustrated in FIGURE 8, is shown inFIGURE 10. In this form the outer tube or shell 200 encloses an innershell or gas passage tube 202 which is of lesser diameter than the outershell. Spaced lengthwise of the inner shell 202 and disposed between theinner shell and the outer tube 200 is a plurality of annular members orrings 204 which form partitions defining sound attenuating chambers 206.The sound attenuating chambers 206 are acoustically coupled with theinterior of the inner shell 202 by means of a comparatively large numberof small openings 208 in the wall of the inner shell.

It is to be understood that in all forms of the invention, the numberand size of the openings in the walls of the inner shells providingacoustic couplings between the inner shells and the sound attenuatingchambers are such as to secure most effective sound attenuation as wellas to promote the flow of exhaust gases through the acoustic couplingsand through the sound attenuating chambers.

It is to be understood that the number of attenuators or soundattenuating units in a tuned exhaust pipe or system and the spacing ofsuch units is dependent in a large measure upon the lengths of soundwaves to be attenuated. The number of sound attenuating units and thespacing between adjacent units is also dependent upon the spacing ofbends or distorted regions of the exhaust pipe or tubular componentsbetween adjacent sound attenuatingunits to avoid interference with frameor structural components of .the vehicle.

It will be apparent that the tuned exhaust pipe system or method of theinvention provides substantial length for sound attenuation so thatsound waves of considerable lengths as well as extremely short soundwaves may be satisfactorily attenuated with a minimum of back pressureespecially as the exhaust gases travels in a generally rectilineardirection and are diverted from such direction only at the regions oftraverse of the gases through the bent or distorted portions orcouplings in the exhaust system and the flow through the soundattenuating chambers.

It is further to be understood that the limitations upon the length ofeach individual sound attenuating unit is only restricted by thenecessary bent or distorted regions fashioned in the exhaust tube toavoid interference with structural components of the vehicle. Throughthe arrangement of my invention, greatly improved sound attenuation hasbeen attained and particularly of the longer wavelengths by reason ofthe substantial path of traverse of the stream of gases throughattenuating media from the exhaust manifold of the engine to a dischargeregion at the rear of the vehicle. Through such arrangement the outertube or exhaust pipe offers substantial heat transfer area so that thegases are more quickly reduced to lower temperatures than has heretoforebeen possible with conventional muffler constructions. F urtherrnore thecontinuous flow of the gases generally in one direction reduces thetendency for carbon particles to be deposited in the attenuating units.

It is apparent that, within the scope of the invention, modificationsand different arrangements may be made other than as herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

I claim:

1. An exhaust gas conveying means for attachment directly to the exhaustmanifold of a vehicle engine including an exhaust pipe of substantiallyuniform diameter throughout its length, a plurality of sound attenuatingmeans arranged in lengthwise spaced relation within the exhaust pipe,each of said sound attenuating means including an outer tube, an innertube of lesser diameter than the outer tube disposed within the outertube, the said outer tube being of a dimension to fit into the interiorcylindrical surface of the exhaust pipe, said outer tube havinglengthwise-spaced inwardly-extending portion-s engaging the innertubeproviding with the inner tube annular sound attenuating chambers, saidinner tube providing a gas passage means and having a wall area providedwith a plurality of comparatively small openings forming acousticcouplings with said annular sound attenuating chambers.

2. The combination according to claim 1 wherein the inner tube is oflesser length than the outer tube.

3. The combination according to claim 1 including means for securing theouter tube to the exhaust pipe.

4. An exhaust gas conveying means for attachment directly to the exhaustmanifold of a vehicle engine including an exhaust pipe of substantiallyuniform diameter throughout its length, a plurality of sound attenuatingmeans arranged in lengthwise spaced relation within the exhaust pipe,each of said sound attenuating means comprising an inner tube and anouter tube with an annular space between said tubes, the inner tubebeing of lesser length than the outer tube, the outer tube being of adimension to snugly fit into the interior cylindrical surface of theexhaust pipe, said outer tube having lengthwisespaced inwardly-extendingportions engaging the inner tube providing partitions subdividing theannular space into annular sound attenuating chambers, said inner tubeproviding a gas passage means, a wall area of the inner tube having aplurality of comparatively small openings forming acoustic couplingswith said annular sound attenuating chambers, the inwardly extendingportions of the outer tube adjacent the ends of said outer tube beingspaced from said ends.

5. The combination according to claim 4 wherein the outer tube issecured to the exhaust pipe by welding.

6. The combination according to claim 4 wherein the inwardly-extendingportions of the outer tube support the inner tube. 7

7. The combination according to claim 4 wherein both end regions of theouter tube are secured to the exhaust pipe by welding.

References-Cited by the Examiner UNITED STATES PATENTS 3,104,735 9/1963Ludlow et al. 18l-36.2

FOREIGN PATENTS 1,351,921 12/1963 France.

RICHARD B. WILKINSON, Primary Examiner.

1. AN EXHAUST GAS CONVEYING MEANS FOR ATTACHMENT DIRECTLY TO THE EXHAUST MANIFOLD OF A VEHICLE ENGINE INCLUDING AN EXHAUST PIPE OF SUBSTANTIALLY UNIFORM DIAMETER THROUGHOUT ITS LENGTH, A PLURALITY OF SOUND ATTNUATING MEANS ARRANGED IN LENGTHWISE SPACED RELATION WITHIN THE EXHAUST PIPE, EACH OF SAID SOUND ATTENUATING MEANS INCLUDING AN OUTER TUBE, AN INNER TUBE OF LESSER DIAMETER THAN THE OUTER TUBE DISPOSED WITHIN THE OUTER TUBE, THE SAID OUTER TUBE BEING OF A DIMENSION TO FIT INTO THE INTERIOR CYCLINDRICAL SURFACE OF THE EXHAUST PIPE, SAID OUTER TUBE HAVING LENGTHWISE-SPACED INWARDLY-EXTENDING PORTIONS ENGAGING THE INNER TUBE PROVIDING WITH THE INNER TUBE ANNULAR SOUND ATTENUATING CHAMBERS, SAID INNER TUBE PROVIDING A GAS PASSAGE MEANS AND HAVING A WALL AREA PROVIDED WITH A PLURALITY OF COMPARATIVELY SMALL OPENINGS FORMING ACOUSTIC COUPLINGS WITH SAID ANNULAR SOUND ATTENUATING CHAMBERS. 